Plural feedback loops instrumentation folded cascode amplifier

ABSTRACT

An instrumentation amplifier configured for providing high common mode rejection is described and includes an input differential stage configured to receive a differential input voltage and a folded cascode amplifying stage configured to receive output current mode signals provided from the input differential pair. A plurality of feedback networks is provided to improve the input stage. The amplifier may operate to provide an enhanced common mode rejection ratio of a single gain block in the instrumentation amplifier. In some examples, the circuitry may have a differential folded cascode amplifying stage which permits high precision and low distortion of amplified signals without degrading the common mode rejection ratio.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/664,777 filed Jul. 31, 2017, now U.S. Pat. No. 10,084,421 issued Sep.25, 2018, the disclosure of which is hereby incorporated in its entiretyby reference herein.

TECHNICAL FIELD

The present disclosure generally relates to audio circuits and tobalanced instrumentation folded cascode amplifiers.

BACKGROUND

FIG. 1 shows a prior art instrumentation amplifier 100 with differentialinput 101 and differential output 102. The instrumentation amplifier 100includes differential input stage 103, with a negative signal receivingtransistor 104 and a positive signal receiving transistor 105 forming aninput pair. The base of transistor 104 receives the inverting input. Thebase of transistor 105 receives the noninverting input. Two amplifiers106, 107 are respectively connected to the outputs of the transistors104, 105. A differential input signal (−IN and +IN) is applied to thebases of transistors 104, 105 of the input differential stage 103. Theoutputs (−OUT and +OUT) of the two amplifiers 104, 105 are connected tothe emitters of transistors 104, 105 of the input differential stage 103through resistors 108, 109, 110.

FIG. 2 shows another prior art instrumentation amplifier 200 withdifferential input (INPUT1 and INPUT2) and differential output (OUTPUT1and OUTPUT2). The base of transistor 204 receives the first inputthrough resistor 208. The base of transistor 205 receives the secondinput through resistor 209. Two amplifiers 206, 207 are respectivelyconnected to the outputs of the transistors 204, 205. The outputs of thetwo amplifiers 206, 207 are connected to the bases of transistors 204,205 of the input differential input through resistors 210, 211. A thirdresistor 212 connects the emitters of the transistors 204, 205.

The instrumentation amplifiers 100, 200 have the drawback of large inputcapacitance. The Miller effect accounts for the increase in the inputcapacitance of the input devices due to amplification of the capacitancebetween the base and collector terminals. The junction capacitancedepends on the applied voltage. Variation in the input capacitance atthe input signal introduces additional distortion. Each transistor 104,105 and 204, 205 of the amplifiers 100, 200 can be replaced with foldedcascode circuit, see, e.g., U.S. Pat. No. 3,473,134. A folded cascodecircuit may have a lower input capacitance, a higher gain, and anabsence of a DC voltage difference between input and output terminalsand may be easier to stabilize. Examples of modified topologies of afolded cascode circuit 300, 400 are shown in FIGS. 3 and 4.

An instrumentation amplifier circuit, having an input stage and anoutput stage, is balanced and preferably exhibit zero common modecomponent in its output signal. Instrumentation amplifier withdifferential output may operate with the floating load or with the loadthat has connection to ground. If the load that has connection to grounddoes not comprise two identical halves, then the output stages supplyunequal currents, generate unequal distortion and produce a common modecomponent. The feedback networks in circuits 100, 200, 300, 400 shown inFIGS. 1-4 have no reference to the ground and do not sense common modesignal.

BACKGROUND

An instrumentation amplifier configured for providing high common moderejection and low distortion is described. The instrumentation amplifiercan include an input differential transistor pair including a firstinput transistor and a second input transistor and configured to receivea differential input voltage at a first feedback input and a secondfeedback input, and to output current mode signals. The instrumentationamplifier can include a folded cascode amplifying stage configured toreceive output current mode signals provided from said inputdifferential transistor pair, the folded cascode amplifying stageincluding first output terminal and a second output terminal. Theinstrumentation amplifier can include a plurality of feedback paths ornetworks, e.g., a first external gain setting circuitry comprising afirst resistor feedback network and a second external gain settingcircuitry comprising a second resistor feedback network.

In an example, the first resistor feedback network may include a firstresistor, a second resistor and a third resistor. The first resistor isconnected between the first feedback input and the second feedback inputof said input differential transistor pair. The second resistor isconnected between the first output terminal of the folded cascode stageand the second feedback input of said input differential transistorpair. The third resistor is connected between the second output terminalof the folded cascode amplifying stage and the first feedback input ofsaid input differential transistor pair.

In an example, the second resistor feedback network includes a fourthresistor, a fifth resistor, a sixth resistor, and a seventh resistor.The fourth resistor is connected between a first signal input and a gateterminal of the first input transistor of said input differentialtransistor pair. The fifth resistor is connected between the firstoutput terminal of the folded cascode amplifying stage and a gateterminal of the first input transistor of said input differentialtransistor pair. The sixth resistor is connected between a second inputand a gate terminal of the second input transistor of said inputdifferential transistor pair. The seventh resistor being connectedbetween second output terminal of a folded cascode stage and the gateterminal of the second input transistor of said input differential pair.

In an example, the instrumentation amplifier may further comprise afirst output buffer and a second output buffer, the first output bufferand the second output buffer being configured to receive a differentialoutput signal from the folded cascode amplifying stage and provide anoutput voltage to the first external gain setting circuitry and thesecond external gain setting circuitry.

In an example, the instrumentation amplifier may further comprise acurrent buffer stage including a pair of transistors, each of the pairof transistors being configured as a current source to a correspondingtransistor of the folded cascode amplifying stage, the current bufferstage being configured to provide a portion of a sum of the outputvoltage to input terminals of a folded cascode stage.

In an example, a dependent current source is connected to the currentbuffer stage. The dependent current source is configured to providecancellation current to input terminals of folded cascode stage.

In an example, the instrumentation amplifier further comprises a firstoutput buffer and a second output buffer, the first and second outputbuffers being configured to receive a differential signal from thefolded cascode amplifying stage.

In an example, a third external gain setting circuitry is proved andcomprises a third resistor feedback network. The third resistor feedbacknetwork includes an eighth resistor connected between an output terminalof the first output buffer and the second feedback input of said inputdifferential transistor pair, and a ninth resistor connected between anoutput terminal of the second output buffer and the first feedback inputof said input differential transistor pair.

In an example, a fourth external gain setting circuitry is provided andincludes a tenth resistor connected between the output terminal of thefirst output buffer and the gate terminal of the first input transistorof said input differential transistor pair, and an eleventh resistorconnected between the output terminal of a second output buffer and thegate terminal of the second input transistor of said input differentialtransistor pair.

An instrumentation amplifier is described and may, comprise an inputdifferential stage configured to receive a differential input voltage ata first and a second input and to output current mode signals, the inputdifferential stage including a first input transistor and a second inputtransistor; a folded cascode amplifying stage configured to receiveoutput current mode signals from the input differential stage; and aplurality of feedback networks operating as gain setting circuitry,wherein a first resistor feedback network of the plurality of feedbacknetworks providing feedback to the first input transistor and the secondinput transistor, wherein a second resistor feedback network of theplurality of feedback networks providing feedback to inputs of the firstinput transistor and the second input transistor.

In an example, the first resistor feedback network includes a firstresistor connected between a first feedback input and a second feedbackinput of the first input transistor and the second input transistor; asecond resistor connected between a first output terminal of the foldedcascode stage and a second feedback input of the input differentialstage; and a third resistor connected between a second output terminalof the folded cascode amplifying stage and a first feedback input of theinput differential stage.

In an example, the second resistor feedback network includes a firstresistor being connected between a first signal input and a gateterminal of the first input transistor of the input differential stage;a second resistor being connected between a first output terminal of thefolded cascode amplifying stage and a gate terminal of the first inputtransistor of the input differential stage; a third resistor beingconnected between a second input and a gate terminal of the second inputtransistor of the input differential stage; and a fourth resistor beingconnected between a second output terminal of the folded cascode stageand the gate terminal of the second input transistor of the inputdifferential stage.

In an example, the instrumentation amplifier further comprises an outputbuffer configured to receive a differential output signal from thefolded cascode amplifying stage and provide an output voltage to thefirst resistor feedback network and the second resistor feedbacknetwork.

In an example, the instrumentation amplifier further comprises a currentbuffer stage including a pair of transistors, each of the pair oftransistors being configured as a current source to a correspondingtransistor of the folded cascode amplifying stage, the current bufferstage being configured to provide a portion of a sum of output signalsfrom the amplifier to input terminals of a folded cascode amplifyingstage; and a dependent current source connected to the current bufferstage, the dependent current source being configured to providecancellation current to input terminals of folded cascode amplifyingstage.

In an example, the instrumentation amplifier further comprises a firstoutput buffer and a second output buffer, the first and second outputbuffers being configured to receive a differential signal from thefolded cascode amplifying stage; and wherein the plurality of feedbacknetworks includes a third resistor feedback network.

In an example, the third resistor feedback network includes a firstresistor connected between an output terminal of the first output bufferand a second input of the input differential stage; and a secondresistor connected between an output terminal of the second outputbuffer and the first input of the input differential stage.

In an example, the plurality of feedback networks includes a fourthresistor feedback network including a third resistor connected betweenthe output terminal of the first output buffer and a gate terminal ofthe first input transistor of the input differential stage; and a fourthresistor connected between the output terminal of the second outputbuffer and a gate terminal of the second input transistor of the inputdifferential stage.

In an example, the instrumentation amplifier further comprises a currentbuffer stage including a pair of transistors, each of the pair oftransistors being configured as a current source to a correspondingtransistor of the folded cascode amplifying stage, the current bufferstage being configured to provide a portion of the sum of the outputsignals to input terminals of a folded cascode stage; and a dependentcurrent source connected to the current buffer stage, the dependentcurrent source being configured to provide cancellation current to inputterminals of folded cascode stage.

Other variations and combinations of the embodiments in the summarysection are with on the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior art circuit.

FIG. 2 illustrates a prior art circuit.

FIG. 3 illustrates a prior art circuit.

FIG. 4 illustrates a prior art circuit.

FIG. 5 illustrates a plural feedback loops instrumentation foldedcascode amplifier, according to an embodiment.

FIG. 6 illustrates a plural feedback loops instrumentation foldedcascode amplifier, according to an embodiment.

FIG. 7 illustrates a plural feedback loops instrumentation foldedcascode amplifier, according to an embodiment.

FIG. 8 illustrates a plural feedback loops instrumentation foldedcascode amplifier, according to an embodiment.

FIG. 9 illustrates a plural feedback loops instrumentation foldedcascode amplifier, according to an embodiment.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

Instrumentation amplifier circuitry is described herein and may be usedfor processing audio signals, e.g., in audio amplifiers, signalprocessors and the like. The circuitry may include a plurality offeedback loops and a differential folded cascode input stage. Thecircuitry may operate to provide an enhanced common mode rejection ratioof a single gain block in the instrumentation amplifier. In someexamples, the circuitry may have a differential folded cascodeamplifying stage which permits high precision and low distortion ofamplified signals without degrading the common mode rejection ratio. Theabove and other advantages of the present disclosure are carried out inone form by a differential folded cascode amplifier circuit, which mayinclude a dependent current source and current followers.

FIG. 5 illustrates an example embodiment of an instrumentation amplifiercircuit 500 with a plurality of feedback loops, e.g., to and from afolded cascode amplifying stage connected to a differential input stage.The differential input stage includes a first transistor 505 and asecond transistor 506. The first and second transistors 505, 506 canform an input differential transistor pair. In an example, thetransistors 505, 506 are field effect transistors. In an example, thetransistors 505, 506 are jfets. The drain of each transistor 505, 506 isconnected to a resistor 503, 504, respectively. The resistor 503 isconnected to the drain of first transistor 505 and a first power source,e.g., a fixed voltage within an audio processing system. The resistor504 is connected to the drain of second transistor 506 and the powersource. The resistors 503, 504 act as loads to transistors 505, 506. Thegate of transistor 505 is connected to the first input through aresistor 501. The gate of transistor 506 is connected to the secondinput through a resistor 502. The source of each transistor 505, 506 ofthe input stage is connected to a constant current source(s) 508, 509,respectively. In an example, the source of the transistor 505 isconnected to the constant current source 508. In an example, the sourceof the transistor 506 is connected to the constant current source 509.The current sources 508, 509 set the current through the input stage,e.g, through the transistors 505, 506. The resistor 507, which can bepart of a feedback network, acts to alter the conductance of the inputstage, e.g., at the transistors 505, 506.

A folded cascode amplifying stage is connected to the differential inputstage and may include a first amplifying transistor 514 and a secondamplifying transistor 515. The drain of the first input transistor 505is connected to an emitter of the second amplifying transistor 515. Thedrain of the second input transistor 506 is connected to an emitter ofthe first amplifying transistor 514. The bases of the first amplifyingtransistor 514 and the second amplifying transistor 515 are connected toa reference terminal, which provides a reference signal to controloperation of the transistors. The collectors of both the firstamplifying transistor 514 and the second amplifying transistor 515 arerespectively connected through resistors 516, 517 to a second powersource, e.g., a fixed voltage within an audio processing system. Theresistors 516, 517 act as loads to the amplifying stage. The resistors503, 504 act as current setting devices that set the current to theamplifying stage. The differential outputs of the circuit 500 from thecollectors of the first amplifying transistor 514 and the secondamplifying transistor 515.

The output signal from the folded cascode amplifying stage is fed backto differential input stage, e.g., through a resistor network. A signalfrom collector of the folded cascode transistor 515 and the output stage520 is fed back to the source of second input transistor 506 through aresistor 511 and to the gate of first input transistor 505 through aresistor 510. The signal from the output stage 520 is fed back to thesource of transistor 506 through a resistor 524 and to the gate oftransistor 505 through resistor 526. The output signal from the cascodedevice 514 is fed back to the source of transistor 505 through aresistor 513 and to the gate of transistor 506 through resistor 512 andthe signal from the output stage 523 is fed back to the source oftransistor 505 through a resistor 525 and to the gate of transistor 506through resistor 527. The sources of the transistors 505, 506 areconnected through resistor 507.

The resistors 507, 511 and 513 can form a first feedback network to thedifferential input stage or a first external gain setting circuit. Theresistors 501, 502, 510 and 512 can form a second external gain settingcircuit. The resistors 510 and 512 can form a second feedback network tothe differential input stage.

FIG. 6 illustrates an example embodiment of an instrumentation amplifiercircuit 500A with a plurality of feedback loops. Like elements to thepreceding embodiments use the same reference numbers. Theinstrumentation amplifier circuit 500A is similar to the circuit 500(FIG. 5) with additional feedback loops and output buffers. Theinstrumentation amplifier circuit 500A includes a third feedback networkand a fourth feedback network from the output to the differential inputstage. A signal from collector of the folded cascode transistor 515 isinput into an output buffer 520 of the output stage. The output buffer520 can be a single input opamp to protect the circuit 500A from andload changes or signals at the output (OUTPUT 1). The signal fromcollector of the second folded cascode transistor 515 is fed back to thesource of second input transistor 506 through the resistor 511. Theoutput signal from the output stage 520 is fed back to the source ofsecond input transistor 506 through a resistor 524. The signal fromcollector of the first folded cascode transistor 514 is fed back to thesource of first input transistor 505 through the resistor 513. Theoutput signal from the output stage 523 is fed back to the source of thefirst input transistor 505 through a resistor 525. The resistors 524 and525 can form a third feedback network. The signal from the output stage520 is fed back to the gate of the first input transistor 505 through aresistor 526. The output signal from the second output stage 523 is fedback to the gate of the second input transistor 506 through a resistor527. The sources of the transistors 505, 506 are connected throughresistor 507. The resistors 524 and 525 can form a fourth feedbacknetwork.

FIG. 7 illustrates an example embodiment of an instrumentation amplifiercircuit 500B with a plurality of feedback loops. Like elements to thepreceding embodiments use the same reference numbers. Theinstrumentation amplifier circuit 500B is similar to the instrumentationamplifier circuit 500 and includes a current follower circuit and adependent current source providing additional feedback to thedifferential input stage. More specifically, additional feedback loopsare provided through summing network 522, a dependent current source 521and two current followers 518, 519. In an example, the current followers518, 519 are common base bipolar devices. The bases of transistors 518,519 are connected to the voltage reference. The voltage reference may bedifferent from the power levels 1 and 2 and may be different that thevoltage reference to the amplifying stage device 514, 515. The collectorof the fifth transistor 518 is connected to the emitter of thirdtransistor 514. The collector of the sixth transistor 519 is connectedto the emitter of fourth transistor 515. Emitters of transistors 518,519 are fed from the paraphrase outputs of dependent current source 521.The current followers 518, 519 and dependent current source 521 aredesigned to compensate for asymmetry in output signal at OUTPUT 1 andOUTPUT2. The summing circuit 522 sums the OUTPUT 1 and OUTPUT2 and sendsa sum signal to control the dependent current source 521.

FIG. 8 illustrates an example embodiment of an instrumentation amplifiercircuit 500C with a plurality of feedback loops. Like elements to thepreceding embodiments use the same reference numbers. Theinstrumentation amplifier circuit 500C is similar to the instrumentationamplifier circuits 500B and 500C, including the current followercircuit, the dependent current source and the output buffer circuit. Theoutput signal from the folded cascode amplifying stage is fed only tothe output buffer stage. More specifically, the collectors of thetransistors 514, 518 of the amplifying stage fed to the single input ofthe buffers 520, 523, respectively. The output from the buffers 520, 523are the outputs (OUTPUT 1 and OUTPUT 2) of the instrumentation amplifiercircuit 500C. The output from the first buffer 520 is fed back to thesource of second input transistor 506 through resistor 511. The outputfrom the first buffer 520 is fed back to the gate of first inputtransistor 505 through resistor 510. The output from second buffer 523is fed back to the source of the first input transistor 505 throughresistor 513. The output from the second buffer 523 is fed back to thegate of the second input transistor 506 through the resistor 512. Thecollector of the fifth transistor 518 of the current follower circuit isconnected to the emitter of third transistor 514. The collector of thesixth transistor 519 of the current follower circuit is connected to theemitter of fourth transistor 515. Emitters of transistors 518, 519 arefed from the paraphrase outputs of dependent current source 521. Thecurrent follower transistors 518, 519 and dependent current source 521are designed to compensate for asymmetry in output signal at OUTPUT 1and OUTPUT2. The summing circuit 522 sums the OUTPUT 1 and OUTPUT2 fromoutput buffers 520, 523 and provides a sum signal to control thedependent current source 521.

FIG. 9 shows a schematic view of an instrumentation amplifier circuit500D. A differential input signal is provided by the input 901. Thedifferential input signal can be an audio signal. The audio signal canbe an analog signal that represents sounds in the range of human hearingor just beyond the ranges of human hearing. A differential input stage903 receives the input signal from the input 901. The differential inputstage 903 outputs a signal to the amplifying stage 905. The amplifyingstage 905 amplifies the signal and outputs the amplified signal to theoutput buffer 907. The output buffer 907 outputs a signal from theinstrumentation amplifier circuit 500D and may provide protection to thecircuit 500D from the load at the outputs. At least a first externalgain setting stage 909 and a second gain setting stage 911 areelectrically connected between the output buffer 907 and thedifferential input stage 903. The first external gain setting stage 909and the second gain setting stage 911 provide discrete feedback networksfrom the output to the input stage 903. A dependent current source 913may be provided to additional control the distortion of the amplifiedsignal. The circuit 500D may operate to provide an enhanced common moderejection ratio of a single gain block in the instrumentation amplifier.In some examples, the circuit 500D may have a differential foldedcascode amplifying stage which permits high precision and low distortionof amplified signals without degrading the common mode rejection ratioat the input stage.

In operation, the first transistor 505 and the second transistor 506 ofthe differential input stage have a cascode (common-base) configurationand their drain terminals connected to emitter of the amplifying(level-shifting) transistors 514, 515, respectively. Using a foldedcascode input stage is believed to address the input capacitance issueof some prior circuit designs. The presently described instrumentationamplifier circuits 500, 500A, 500B, 500C obtain a negative feedback byconnecting the output from the amplifier (output stage) back to thesources of the first and second transistors of the input differentialstage through resistor networks. In an example, a first network (e.g.,the resistor 507 and the resistors 513 and 511) provides a feedbacksignal to the differential input stage. In an example, a second networkdirects the output from the amplifier (output stage) back to the gatesof the first and second transistors of the differential input stage(e.g., through the resistor 510 and the resistor 512). Additionalfeedback loops are provided through the summing network 522, thedependent current source 521 and the two current followers 518, 519.

The present circuitry described herein may have a plural feedback loopsin instrumentation amplifier with differential folded cascode inputstage. The present circuitry may operate to provide an enhanced commonmode rejection ratio of a single gain block instrumentation amplifier.The present circuitry may have a differential folded cascode amplifyingstage which permits high precision and low distortion of amplifiedsignals without degrading common mode rejection ratio. The above andother advantages of the present disclosure are carried out in one formby a differential folded cascode amplifier circuit which may includeadditional dependent current source and current followers.

The present disclosure describes feedback networks formed fromresistors, it will be within the scope of the present disclosure to usea plurality of resistive elements in place of a single illustratedresistor.

The present disclosure uses the term stage to represent variousprocessing stages in circuitry. The stages may include a plurality ofdiscrete electrical components to provide the signal processing of adescribed stage.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

What is claimed is:
 1. An instrumentation amplifier configured forproviding high common mode rejection and low distortion, saidinstrumentation amplifier comprising: an input differential stageconfigured to receive a differential input voltage at a first and asecond input and to output current mode signals, the input differentialstage including a first input transistor and a second input transistor;a folded cascode amplifying stage configured to receive output currentmode signals from the input differential stage; and a plurality offeedback networks operating as gain setting circuitry, wherein a firstresistor feedback network of the plurality of feedback networksproviding feedback to the first input transistor and the second inputtransistor, wherein a second resistor feedback network of the pluralityof feedback networks providing feedback to inputs of the first inputtransistor and the second input transistor.
 2. The instrumentationamplifier according to claim 1, wherein the first resistor feedbacknetwork includes: a first resistor connected between a first feedbackinput and a second feedback input of the first input transistor and thesecond input transistor; a second resistor connected between a firstoutput terminal of the folded cascode stage and a second feedback inputof the input differential stage; and a third resistor connected betweena second output terminal of the folded cascode amplifying stage and afirst feedback input of the input differential stage.
 3. Theinstrumentation amplifier according to claim 1, wherein the secondresistor feedback network includes: a first resistor being connectedbetween a first signal input and a gate terminal of the first inputtransistor of the input differential stage; a second resistor beingconnected between a first output terminal of the folded cascodeamplifying stage and a gate terminal of the first input transistor ofthe input differential stage; a third resistor being connected between asecond input and a gate terminal of the second input transistor of theinput differential stage; and a fourth resistor being connected betweena second output terminal of the folded cascode stage and the gateterminal of the second input transistor of the input differential stage.4. The instrumentation amplifier according to claim 1, furthercomprising an output buffer configured to receive a differential outputsignal from the folded cascode amplifying stage and provide an outputvoltage to the first resistor feedback network and the second resistorfeedback network.
 5. The instrumentation amplifier according to claim 4,further comprising: a current buffer stage including a pair oftransistors, each of the pair of transistors being configured as acurrent source to a corresponding transistor of the folded cascodeamplifying stage, the current buffer stage being configured to provide aportion of a sum of output signals from the amplifier to input terminalsof a folded cascode amplifying stage; and a dependent current sourceconnected to the current buffer stage, the dependent current sourcebeing configured to provide cancellation current to input terminals offolded cascode amplifying stage.
 6. The instrumentation amplifieraccording to claim 1, further comprising: a first output buffer and asecond output buffer, the first and second output buffers beingconfigured to receive a differential signal from the folded cascodeamplifying stage; and wherein the plurality of feedback networksincludes a third resistor feedback network.
 7. The instrumentationamplifier according to claim 6, wherein the third resistor feedbacknetwork includes: a first resistor connected between an output terminalof the first output buffer and a second input of the input differentialstage; and a second resistor connected between an output terminal of thesecond output buffer and the first input of the input differentialstage.
 8. The instrumentation amplifier according to claim 7, whereinthe plurality of feedback networks includes a fourth resistor feedbacknetwork including: a third resistor connected between the outputterminal of the first output buffer and a gate terminal of the firstinput transistor of the input differential stage; and a fourth resistorconnected between the output terminal of the second output buffer and agate terminal of the second input transistor of the input differentialstage.
 9. The instrumentation amplifier according to claim 8, furthercomprising: a current buffer stage including a pair of transistors, eachof the pair of transistors being configured as a current source to acorresponding transistor of the folded cascode amplifying stage, thecurrent buffer stage being configured to provide a portion of the sum ofthe output signals to input terminals of a folded cascode stage; and adependent current source connected to the current buffer stage, thedependent current source being configured to provide cancellationcurrent to input terminals of folded cascode stage.
 10. Aninstrumentation amplifier, comprising: an input differential stageconfigured to receive a differential input voltage and to output currentmode signals; a folded cascode amplifying stage configured to receiveoutput current mode signals from the input differential stage; and aplurality of feedback networks operating as gain setting circuitry,wherein a first resistor feedback network of the plurality of feedbacknetworks providing feedback to a first input transistor and a secondresistor feedback network of the plurality of feedback networks.
 11. Theinstrumentation amplifier according to claim 10, wherein the inputdifferential stage receives the differential input at a first and secondinput, and the input differential stage includes a first inputtransistor and a second input transistor, wherein the first resistorfeedback network includes: a first resistor connected between a firstfeedback input and a second feedback input of the first input transistorand the second input transistor; a second resistor connected between afirst output terminal of the folded cascode stage and a second feedbackinput of the input differential stage; and a third resistor connectedbetween a second output terminal of the folded cascode amplifying stageand a first feedback input of the input differential stage.
 12. Theinstrumentation amplifier according to claim 10, wherein the secondresistor feedback network includes: a first resistor being connectedbetween a first signal input and a gate terminal of the first inputtransistor of the input differential stage; a second resistor beingconnected between a first output terminal of the folded cascodeamplifying stage and a gate terminal of the first input transistor ofthe input differential stage; a third resistor being connected between asecond input and a gate terminal of the second input transistor of theinput differential stage; and a fourth resistor being connected betweena second output terminal of the folded cascode stage and the gateterminal of the second input transistor of the input differential stage.13. The instrumentation amplifier according to claim 10, furthercomprising an output buffer configured to receive a differential outputsignal from the folded cascode amplifying stage and provide an outputvoltage to the first resistor feedback network and the second resistorfeedback network.
 14. The instrumentation amplifier according to claim13, further comprising: a current buffer stage including a pair oftransistors, each of the pair of transistors being configured as acurrent source to a corresponding transistor of the folded cascodeamplifying stage, the current buffer stage being configured to provide aportion of a sum of output signals from the amplifier to input terminalsof a folded cascode amplifying stage; and a dependent current sourceconnected to the current buffer stage, the dependent current sourcebeing configured to provide cancellation current to input terminals offolded cascode amplifying stage.
 15. The instrumentation amplifieraccording to claim 10, further comprising: a first output buffer and asecond output buffer, the first and second output buffers beingconfigured to receive a differential signal from the folded cascodeamplifying stage; and wherein the plurality of feedback networksincludes a third resistor feedback network.
 16. The instrumentationamplifier according to claim 15, wherein the third resistor feedbacknetwork includes: a first resistor connected between an output terminalof the first output buffer and a second input of the input differentialstage; and a second resistor connected between an output terminal of thesecond output buffer and the first input of the input differentialstage.
 17. The instrumentation amplifier according to claim 16, whereinthe plurality of feedback networks includes a fourth resistor feedbacknetwork including: a third resistor connected between the outputterminal of the first output buffer and a gate terminal of the firstinput transistor of the input differential stage; and a fourth resistorconnected between the output terminal of the second output buffer and agate terminal of the second input transistor of the input differentialstage.
 18. The instrumentation amplifier according to claim 17, furthercomprising: a current buffer stage including a pair of transistors, eachof the pair of transistors being configured as a current source to acorresponding transistor of the folded cascode amplifying stage, thecurrent buffer stage being configured to provide a portion of the sum ofthe output signals to input terminals of a folded cascode stage; and adependent current source connected to the current buffer stage, thedependent current source being configured to provide cancellationcurrent to input terminals of folded cascode stage.